Erythropoietin levels in endocrinopathies
Emilie Klein, Julie Brossaud, Blandine Gatta & Jean-Benoît Corcuff
Erythropoietin (EPO) is an oxygen-regulated hormone promoting the differentiation of erythroid progenitor cells. Apart from hypoxia, few data is available about EPO release by secretagogues including hormones. This retrospective study evaluated serum EPO concentrations in serum leftovers from subjects routinely investigated with various endocrine disorders displaying: peripheral hypothyroidism or hyperthyroidism, acromegaly, endogenous Cushings syndrome or non secreting pituitary tumour. Patients with the latter, chosen with no deficiency in the thyrotroph, gonadotroph, somatotroph and corticotroph axis, were included as a control group.
EPO levels were all above the normal low limit - an important point as a low EPO level is a sensitive and specific diagnostic test of polycythemia vera. All 12 but 1 patients with elevated EPO levels had some reason to present, at least mildly, hypoxemia (myocardiopathy, tobacco smoking).
No statistically significant relationship was evidenced between a given hormone and EPO concentrations. In patients with thyroid dysfunction or Cushings syndrome or non secreting pituitary diseases, multiple regression analysis showed a statistically significant relation between EPO and Hb (P<0.05) but no significant influence of free T3 or T4 or free urinary cortisol (in patients with thyroid dysfunction or Cushings syndrome). Interestingly, in patients with acromegaly, multiple regression analysis showed no significant relationship between EPO and Hb or IGFI or GH (i.e. the normal EPO- Hb relationship was abolished). This may reflect a dual action of GH and/or IGFI on erythroid progenitors proliferation as well as on EPO synthesis.
In conclusion, EPO is not noticeably modified by common endocrine disorders although GH and or IGFI may alter EPO relationship with blood haemoglobin concentration. This point may deserve further clinical investigation.